Differential transmitters communicate information by providing complementary signals from the transmitter to the receiver. Differential signaling may reduce the effects of electromagnetic noise on signal integrity by detecting the difference between the signals. Some differential transmitters (e.g., tristate transmitters) may also enter a high impedance state, where no signal is transmitted. Many traditional differential signaling circuits include termination circuits, such as termination resistances, coupling the complementary signal lines to ground. In such circuits, when the differential transmitter enters the high impedance state, any residual charge on the signal lines discharges to ground (or some other non-ideal leakage voltage). That is, during the high impedance state, the differential signal on the signal lines is lost as both signals discharge to the termination voltage (e.g., ground).
Differential signaling is common in many memory systems. For example, differential signaling may be used to provide data strobe signals to a data output buffer. A memory die may, for example, provide read data to an output buffer on a logic die and a differential strobe signal to a differential receiver on the logic die. The differential receiver may then provide an output strobe signal based on the received differential strobe signal. Often, several memory die, each one having its own differential transmitter, are stacked and coupled to a single differential receiver located on the logic die. When the transmitter of a particular memory die is not in use, it enters a high impedance state, effectively removing it from the circuit.